Topic 6
Storage Pits

In the West Pasture, several storage pits have been found and excavated. Many of them were located close to the houses, while others were found in isolated areas farther away. The contents of the storage pits have been documented and studied, and this reveals much about human behavior.

Most of the sediments recovered within these pits have gone through the process called flotation, allowing the carbonized remains to be separated and collected. The results identified charred corn as one of the foods utilized for their subsistence. Corn is a seasonal crop, and one must be diligent about processing and storing corn if it to be used during different seasons, especially the winter months.

The shape of these pits varies, but a common shape is described as “bell-shaped”. That being the mouth or top of the pit at the ground surface is narrow for a few inches down, then expands outward ending with a flat bottom. Logic tell us, the size of the pit (container) is relevant to the amount of product to be placed inside. This doesn’t necessarily relate to the amount of product produced as the feature relates to the individual’s needs. The various sizes may relate to nearness to the residence, population of consumers, including perhaps communal storage.

Two average sized storage pits were exposed near Hank’s house. Pit feature 3, approximately 1 meter east outside the entrance, contained refuse or discarded artifacts suggesting the original contents had been consumed and the pit became the trash dumpster. A second pit, called Feature 4, was discovered immediately west of and about 2 meters (6 ft, 8 inches) behind Hank’s house. After it was abandoned, this storage pit was not used as for discarding trash. Rather, it appears that this pit was left empty and open at the top, and it collapsed in on itself.  

Feature 4, an abandoned bell-shaped pit found 2 meters west of Hank’s house. Note the dark brown fill in the upper pit and the brown layered fill in the lower part of the pit. These layers tell a story about the abandonment of the pit.

Feature 4, abandoned, provided evidence related to the preparation of these storage pits. There are many organisms that live and burrow underground. If the people who stored produced foods intended to have the product later in time, they needed some mechanism for protecting it from these underground pests. The plastering of all interior surfaces provided a barrier which deterred and detoured these burrowing animals which no doubt would destroy the contents.

Closeup view of the lower sediment fill in the bottom of the Feature 4 storage pit. The archeologist is pointing to a thin undulating layer of clay plaster that is about 15 cm above the bottom of the pit. This ribbon-like layer represents wall plaster from the sides of the pit that collapsed down into the pit.

Underground storage pits (also called cache pits) are extremely beneficial to archeologists when we study prehistoric farming cultures and their material remains. Based on ethnographic evidence, we know that many historic Plains cultures that practiced farming used underground storage pits for storing dried crop foods, especially corn, beans, and squash. Most Plains storage pits were cylindrical or bell shaped (expanding downward in the shape of a bell), and these are the two common pit shapes we find in the West Pasture sites. We also see different use and abandonment life cycles represented among the West Pasture storage pits.

While its original function was for food storage, various things might happen to a storage pit after it was abandoned. Here are three scenarios: (1) Perhaps the most common scenario is that pits were opened to retrieve the food and then they were backfilled with trash. Pits were generally abandoned when the side walls of the pit became old and weak or when burrowing rodents discovered the pits. (2) If a pit was filled with stored plant foods but it was never reopened to retrieve the food, then the organic materials would decay inside and leave a dark organic rich soil and residue behind. (3) If a pit was left open and empty, it would be exposed to the elements and eventually collapse, which is what we see with Feature 4.

The excavation of Feature 4 revealed a ribbon-like band of clay plaster preserved in the lower pit fill but still about 15 to 20 cm above the bottom of the pit. This undulating plaster layer was found laying on relatively sterile windblown sand, and it had darker organic fill above it. This evidence tells us several very important things: (1) The pit was indeed left open and had begun to fill in naturally; (2) The side walls and bottom of the pit were intentionally plastered with clay, most likely to help deter burrowing insects and rodents; (3) The upper side walls collapsed into the open pit; and (4) additional sediment and organic materials were deposited into the collapsed pit depression.

A cross-section of a bell-shaped storage pit filled with crop foods and capped. This pit was described by Buffalo Bird Woman, a Hidatsa, and illustrated in the 1917 book Agriculture of the Hidatsa Indians: An Indian Interpretation by Gilbert Livingstone Wilson.

One final interpretation may be offered for the West Pasture Plains Villagers based on the consistent presence of underground food storage pits found near their houses. A broad survey of ethnographic accounts indicates that when Native American groups used subterranean food storage pits, they did so to hide their food surplus because they would periodically abandon their villages, usually to go on extended buffalo hunts. Underground storage pit were used to hide critical food stores from other bands or tribes, and this was an important part of the survival strategy for the West Pasture peoples.